Friction clutch



Sept. 4, 1934. c, w. CHAPMAN 1,972,643

FRICTION CLUTCH Filed Oct. 14. 1931 2 Sheets-Sheet l M mw l @56K/MM,

SePt- 4, 1934. c. w. CHAPMAN 1,972,643

FRICTION CLUTCH Filed oct. 14. 1931 z'sheets-sheet 2 Elven to Y.'

r the driven member. In a brake the 'drivenL1 mem"- merels ndieete like Parts.

VPatented Sept'. 4, 1934 Q i UNITED kST'ATES :PATENT OFFICE v Y if FnrcTroNoLUTcH e Charles 'WallaceChapmam Strood, Kent, England, assigner of one-half to FrancisvArthur Perkins, Kent, England "9 claims. 101192-105) H v l This invention is for improvements .in.or.re j Figure 6 shows amodification of the construclating to torque transmitting. devicesvofthe type tionshown in Figures 4 and 5; e, comprising a driving member anda driven rnem- Y AFigure '7 shows a still further modification;

ber, and one ormore clutchelements pivoted to e Figure L 8; showsin detail a' clutch according e the driving member and arranged to;bethro'wri tol this invention', this "figurebeing taken on .Ge

by centrifugal force 'intov engagement with'the the line 8--8 in Figure 9; and i l driven member, which elements areso arranged Y 4 Figure 9 is a section taken on the line 9^9 in and dimensioned that normalrotationv of the Figure 8. 1" 1 f e 'Y driving member tends towedge them toward e Throughout thS description' like reference nuber may be stationary and in a clutch thevdriven f The clutch shown diagrammatically in Figmember will rotate. This invention provides a ure 1 consists of a drivingr member 10 provided torquetransmitting device of the type specied with a'boss 11 and a druni"(or driven member) wherein each clutch element'comprisesfan arm 12.. Pivoted on' pins, 13 `on the boss 11 are a.

n V pivoted to one member and a shoe pivoted to the number of arms 14, two onlyv of which are shown. 70

" free encl oi the arm and arranged to make con- The clutch arranged for rotation ofthe drivtact with the'other member, and wherein the ing member 10 in'ananticlockwise direction, and tangent of the angle which is included between the arms 14 extend forwardlyand outwardly a line joining the pivot of each arm to thedrivin the direction of rotation. To the free end ing member tothe point of. contact of `its shoe of 'each arm a clutch-shoe `15; faced with fric- 75 with the driven member (or if contact is'.made tion material, is pivoted at 16. A tension spring i over a llarge varea then with Ythe centerof pres- 17 extends'between the pivot 13 of one arm 14 sure) Vand a line normal `to the surface of the and the pointV on the adjacent arm midway in driven member at the point of contact (or cen- 'the length of the latter. These springs thereter of pressure) is greater than the maximum fore Vvtend to fold the arms "14 down about the e0 kinetic :2o-efficient of friction. centre of the driving member 10.

ABy keeping the angle greater` than the kinetic The operation of the torque transmitting device cofefcient of friction we are enabledto avoid is asvfollowsz-Assuming the driving member to ShOCk in taking 11p the d IVe and yet retain the lbe rotated in an anticlockwise' direction and the valuable feature that thepressure of the driving driven member to be stationary, the driving 85 element on the shoes tends to assist Ythe cen- `member is speeded up until the centrifugal force trifugal force in taking' up the drive; Moreacting on the clutch elements (each constituted over, by this means, on verrlmnrlg a freeby a pivoted arm and shoe) is lsufficient to overwheel actionis facilitated. The present invencome the force exerted by the tension springs tion does not extend t0 eases Where the Opereabove mentioned.'` These clutch elements will 9o tive direction of rotation is such that the driving tnen be thrown outwards into engagement with member tends t-O'pull the Shoe behind it, as in the interior of the drum. The drum is theresuch cases no wedgirlg aCOn takes plaeefore caused to tend torrotate (in the case of a By the expression kinetic co`efcient 0f `fleclutch) vand due to the resisting torque andfto 40 tien iS meent that Ce-eent- 0f friction 0f the 'difference in speedsbetween the driving and 95 the materalS used Whieh ObterlS When there S Ydriven member, the clutch elements will tend relative movement between the tWO Surfaces (to wedge intorm engagement withthe drum; Which are irl fretenel engagementthe greater the resisting torque the' tighter will Various constructions of clutches .according to hey be wedged into engegennern;l 1f eti-any pethis invent/ieri Will vlleW'be described in detail riod the driven memberover-runs the driving 100A byfWay 0f eXample With refererleefterlieaeeemmember then the frictional drag will decrease rallying drawings, in which:- this wedging actmnand if thespeed of `the driv- Figure 1 shows one construction loi? clutch; ing member drops below a certain predeter- Figure v2 shows a modied construction; mined value at which the Vcentrifugal force on e Figure'Sis a `detail'showing an alternative the clutch elementsfequals the force exerted 105 ,method of mounting the Sh0e:15 Slidebly `With .by the above `mentioned tension springs, rthen vrespect of the pin v113 in the'arrangementshown the clutch elementswill be moved completely in Figure 2; Y e 'i i l L* out of engagement with the drum, and the clutch Figures 4-and `5v show in elevation and in sec- AWilla'ct as a freewheel. 4

5 5 Vtion respectively av further modiiication; f. e 1t can be 'shown the tangent/*ofthe 110 angle included between the center lines of the thrust in the arms (which are almost coincident with the lines joining the pivots of the arms with the centers of pressure) and the radius of the drum at the point of contact of this thrust line and the drum is greaterthan the maximum kinetic coefficient of friction,V then theffrictional force set up is a function of speed of the driv ing member so that the torque transmitted increases with engine speed and the drive is takni Y the, inner. end of which is spigotted in a ball-bearup gradually and without shock. i

If the tangent of the angle above-mentioned is between the static and 'kinetic .co-eiicients of. Y y

"shaft" ltfwd'to theilywheel 28 by pivot-pins 130; the lattrare equally spaced varound the centre friction of the materials used, Ethen the drive w'ill be taken up gradually and without shock, but the drive willnot slip when ronce itis engaged.

If the tangent of the angle iis greater both the kinetic and static co-effioientsnof friction, not only will the drive be taken up 'grade uallyV ,and without shock Abut overload will cause the clutch to slip, 'tt/nich "is on advantage fin loertain cases. y

The device Yshown i'n Figure 1 may be fu'tilized as a brake, infwhic'hlcaseftl'ie driven menibier will be anchored,` say tfo fthe rarnwo'ik or "chassis oa vehicle. ,A V f' n In themodication shown Vin Figurel 2 the device is .arrangedto take up the drive in 'thecase o'fa clutch', or to exert a braking leiort'i'nthe case of the brake, in either.clockwise or anti# clockwise directions foi -rotation. vTo this end each shoe 15 is pivoftedto ltwo arms :114. At their inner ends these arms areprovided with slots 25 in which pivot-.pins `113 attached -to the central boss `1`1' of the drivingv member 'are "onlgaged. The clutchshoe .drawn 'down out of Contact with the drum '12 by means fof a "radial tension spr-'ing 1'8. "It will be seen that' 'in one direction of rotation one Varmvv-ill takejthe thrusts and the other arm slide freely on its pin 113, 'While in the reverse `direction .of rotatinthese vvconditions will be reversed.

instead of the slotted arms shown in Figure 2, an arm such .as that shown in Figunef inay 'be used. This arm consists o 'f fa cylinder 19 within which a plunger 2D is'slida'bly mounted, l tl'ils plunger being spring-pressed towards the bottom end of the I'cylinder by`a compression 'spring 2'1. lhe cylinder V19 will be pivoteii to the bossll and ,shaft of. the` .plunger '2 0 to the shoe '15, or li'rifc'e versa. n Y Q In the modication shown in Figures @and 5, for each brake shoe 15 fa bfe'llf'crahk le'i'zei` 2 2 is Vpivot'ed on the boss `11 of the drivihg'iiemb'ei'. vOne end of this bell-crank lefv'er isy joined by 'a radial tension spring 23 to th e shoeV 1*'5, whilethe other is in contact with a'icollr 2 4 which *i'sslidablynounted on the driving i'nenber. "It will be seen 'that by moving the collar 24 'along the kdriving member, the sp'rfing tension tending to hold the shoe o'utjo engagement (and acting inopposition to the centrifugal forceiof the "shoe 'and its arm) kmay be varied and 4therefore a oei-tain mann ual control of the operation o theclutch 'or brake may bo exercised. y Figure 6 is a modification or tno construction s'ho'wnr in Figures 4 and 5 in whi'chtwosjlotted arms '114 aroused, so thatxthe :clot-chiot brake W'ill operate' automatically in eit'hfer 'direction off vrotation. i s j In the "modinoationsnown uiagrammaticaiiy in Figure 'I each shoe 15 isf'movedout into tingagemntwith 'the 'drum '12 by means of a 'cani 27, thus providing mechani'srii, o1 bringing these "Y twopa'rts into engagement iat-low speeds; )The shoes are biased away from the drum by means of a tension spring 26 which extends between the pivot 13 of one arm 14 and the pivot 16 of the adjacent shoe.

Figures and 9 show in detail a clutch suitable tor use an automobile. This clutch comprises Ia iiriving shafti-llbolted tov a, flywheel 28 and a driven member in the form of a drum 12 located concentrically within the flywheel. The drum 12 ris-tnounted for slding movement upon a shaft 29,

ing 3l) supported in a centre boss 11 of the driving This Acentre boss is bolted to the fboss l1v` and parallel to its axis, and upon each of anafrm T5214 is pivoted (upon antifriction bearings) .,fAs viewed in Figure 9, the driving fineiiibi is arranged for rotation in an anticlock- Wise direction and thearms 214 extend outwardly and -forviafd'iy in thedireetionof rotation.' 'on trie omtrend of each arm 214 is a rearwardly im clinedieitterfsion 8; when the' islfuiiy extended; aputsthe central boss 1i. Between 'each extension :Brand the central bo'ss a compression' spring 38-isfpiaoedi nt the end'foi "earih' arm 4'2711i ja link Blcon'si-sting of two cheeks, one on eachiside of the arm) Yis 'pivot-,ed on anti- *frictlonbeaiings Jon a Ipivivt-pin 35. Each -ch'ee'k terminates on-the inner sise ofthe apivot es in o '105 oaianoefweignt 36, Ea'chfpsir ottomano-weights isljjoin'ed by La stopepin T37 which passes through al noie '38 in 'the appropriate larm y2111.1 'Between 'the outer` ends-of each pair of 'cheeks constitute round tneboss i1 and tue shoes '15 heid clear:

of the drum y1.2. thefszpeed increases to a 'value 'iat 'which centrifugal force overcomes 'one pressure or thesprngs 3`3ythe arms ny out- 'Wards-until vtrie shoes-make with the tintin.vv v'ist Jperiod the inner'gextensions '3'2 oi tire 'arms 'dotno't touch 'tnofentm boss '1l of the fdriving 'inemben Y'ir-he Yfictionai nog oiture .shoes .'15 pressesI the stopepin's '3'7 against tneinn'er edge fof their appropriate holes 38 1in the `-arms '214, andthe iinksisii Yand the ams 214 transmit Vithe 'drive solidly. :By jrnaking the balance-weights 'not -(nnte `'suiii'cieritly heavy to countebalaiicethe 'lnksanl the shoes, centrifugal ror'roe win-"tono .tencia the stop-pins "si: in fthe position fsh'ovngf Alternatively, or additionallyt a light spring 4o (shown 'in 'chain-dotted lines in Figure "9) may be employed 'for this ugiro'r'oe :tioifgjaiine radio1 from the 'centre of the driving' ineinbertmough `the axis of the pin '35 isgreater than the'ilioinent "'(a'iso' taken about this' 'pini` o the kurfivin'g' thrust along' the `centre line oifj'trio @mouthed the arm anti thoinks win ten to straighten outuntn the inner foxof 'the 'afm makes: oontaot with tno drumrigrorsmooth terigjagentei fit-rana teaoifsup of the invertito ytangeintof# the angie someto the line joining the centres of pins 130 and 39 and the radial line through the pin 39 is greater than the maximum kinetic co-efiicient of friction.

In order to provide for a non-slipping or self-locking drive when the link 34 and the arm 214 are in the fully extended position, the angle between the center line of link 34 and a radial line through the center of pin 39 is in this case made less than the limiting angle of friction.

The drum 12 is provided` with a flange 41 faced with friction material which by means of the pedal 42, compression spring 43 and thrust bearing 44 may be pressed against the central flange 45 of the flywheel 28, in order that the engine may be used as a brake.

It will be appreciated that all the constructions described above with reference to the accompanying drawings embody the feature of lcentrifugal application of the shoes to the drum assisted by servo action of the shoes, and they all embody that relationship between the kinetic co-emcient and the tangent of the angle included between the f thrust line (or the line joining the center of pressure and the pivot of the link) and the normal line, specified herein.

Iclaim:

l. A friction coupling, comprising a drum and a boss within it independently rotatable about the same axis, arms pivoted to said boss around its centre, each arm lying on a non-radial line, a link pivoted to the end of each arm, a shoe pivoted to the end of each link and a balance Weight for the shoe on each link, whereof the centre of gravity of each shoe, link and weight coincides approximately with the pivot of the link. i

2. In a friction coupling the combination of a driving member and a driven member independently rotatable about the same axis, at least one clutch shoe pivoted to one member for movement into frictional engagement with the other member by centrifugal action, said shoe wedging in one direction of relative rotation be tween the two members and tending to free in the other direction, auxiliary friction surfaces on the two members, and means for moving said members axiallyin relation .one to the other to engage said auxiliary surfaces.

3. A friction coupling engaging and disengaging automatically with increase and decrease in speed of rotation, comprising the combination of a drum and a rotatable boss concentric therewith, a number of arms pivoted to said boss and extending forwardly and outwardly, shoes attached one to the outer end of each arm and movable by their own centrifugal force into frictional engagement with the drum, and an extension on the inner end of each arm movable into contact with the boss to limit the outward movement of the shoe.

4. In a friction coupling the combination of a drum and a boss concentric therewith and rotatable independently of it, a number of arms pivoted to the boss for movement about axes spaced on each link on the opposite side of the pivot of the link from the shoe whereof the angle, included between a radial line from the axis of rotation through the pivot of the shoe and the line through the pivot of the shoe and the pivot of the arm, is greater than the limiting angle of friction.

5. In a friction coupling the combination of a drum and a boss concentric therewith and rotatable independently of it, a number of arms pivoted to the boss for movement about axes, spaced around but parallel to the axis of rotation of the boss, said arms extending outwards in nonradial attitudes, a link pivoted to the free end of each arm, a shoe pivoted to the free end of each link and movable by a centrifugal action into frictional engagement with thedrum, and a balance weight on each link on the opposite side of the pivot of the link from the shoe, whereof the angle, included between the centre line of a link and a radial line through the pivot of the shoe, is less than the limiting angle of friction.

6. A friction coupling as claimed in claim 4, wherein an abutment is provided upon each rof the arms pivoted to the boss to contact with a portion moving with theboss and limit movement K of the arm under the influence of centrifugal force exerted upon the link beyond a predetermined extent.

" 7. A friction coupling as claimed in claim 4,

wherein'an abutment is provided on each of the arms pivoted to the boss to contact with a part moving with the boss and limit movement of the arm relatively to the boss beyond a predetermined extent and wherein the arm is urged away from the abutment by a spring.

8. In a friction coupling the combination of a drum, a boss concentric therewith and rotatable independently thereof, a plurality of arms pivoted to the boss to move about axes spaced around but extending along the axis of rotation of the boss, said arms extending outwards in non-radial attitudes, abutments upon said arms to engage a part rotating with the boss and limit outward movement of the arms to a predetermined extent and shoes pivotally mounted upon said arms to cooperate with the drum under the influence of centrifugal force.

9. In a friction coupling the combination of a drum, a boss concentric therewith and rotatable independently thereof, a plurality of arms pivoted to the boss to move about axes spaced around but extending along the axis of rotation of the boss, said arms extending outwards in non-radial attitudes, abutments upon said arms to engage a part rotating with the boss and limit outward movement of the arms to a predetermined extent, shoes pivotally mounted upon said arms to cooperate with the drum under the influence of centrifugal force and spring means for opposing said outward movement of said arms.

CHARLES WALLACE CHAPMAN. 

